Recording of electrical impulses



July 30, 1940. F. E. RUNGE RECORDING OF ELECTRICAL IMPULSES Filed Dec.22, 1937 Patented July 30, 1940 UNl'TED srATss 2,209,664 RECORDING FELECTRICAL IMPULSES "Frank E. Runge, Oaklyn, N. 1, assignor to RadioCorporation of America, a corporation of Delaware Application December22. 1937, Serial N is1 '6 s- (ol. Ha -100.3 3 V This invention relatesto the recording of electrical impulses such as those of audiofrequency, and has for its principal object the provision of an improvedapparatus and method of operation 5 which are inexpensive and simple ascompared to those heretofore available.

A distinguishing characteristic of the invention is a linear opticalsystem which avoids the need of a vibratible mirror or the like. To thisend a small lens interposed in the path of the recording light beam isvibrated in response to the impulses to be recorded. While the inventionis illustrated as applied to the recording of a push-pull type ofrecord, it is apparent that it is readily adaptable to other types ofrecord.

The invention will be better understood from the following descriptionconsidered in connection with the accompanying drawing and its scope isindicated by the appended claims.

Referring to the drawing,

Figure 1 illustrates a recording system wherein the vibratible mirror ismounted at the end of a vibratible armature which is energized inaccordance with the impulses to be recorded,

Figure 2 illustrates a resilient type of support for the vibratiblelens,

Figure 3 illustrates a bell crank type of support for the vibratiblelens, and

Figure 4 shows the vibratible lens as provided with a pivotal mount andarranged to be slightly rotated in response to movement of itscooperating armature.

In the system of Fig. 1, light from an exciter lamp ii! is projectedthrough a lens H, the aper- 35 tures of a plate 12, a vibratible lens13, a lens 14, the light slit of a plate l5 and lenses [6 and I! to aphotographic record i8 such as a sound motion picture film. It will benoted that the apertures l9 and 20 each have the form of a triangleprovided with an extended base to prevent the disturbance caused byovershooting of the beams and with slit-like extensions or tail at theirpeaks to ensure better definition of the record.

Vibration of the lens 13 in accordance with the impulses to be recordedis effected by means of an armature 2| which is mounted in a magneticfield produced by a magnet 22 and is surrounded by a coil 23 to whichthe impulses to be 50 recorded are applied. The lens l3 images theapertures l9 and 20 on the plate l5 as indicated at 24 and 25. When theimpulses to be recorded are applied to the coil 23, the lens I3 isvibrated in accordance with these impulses, the images 24 and 25 aresimilarly vibrated transversely of the light slit 2t and there isproduced on the sound track 21 of the film l8 awell known type of pushpull record. It will, of course, be understood that a suitable filmdrive mechanism is provided for moving the film transversely of thelight 5 slit at a substantially constant speed.

The vibratible lens mount of Fig. 2 differs from that of Fig. 1 in thatthe lens 13 is mounted in a resilient support 28 which is attached tothe magnetic structure 22 by means of screws 29 and 10 washers 39 whichmay be of brass or other suitable non-magnetic material. It will benoted that the end of the armature 2! is attached to the transversemember of the support 28 and imparts to this support and t0 the lens l3a motion 15 which is substantially linear. This structure has theadvantage that it may be so designed as to provide a desired responsecharacteristic. Thus it may be made to have the natural vibration periodmost suitable for the conditions under 20 which it is operated. Thenatural vibration period may, of course, be Within or without the signalfrequency range depending on the result desired.

The lens mount of Fig. 3 differs from those of 5 the previous figures inthat the lens [3 is mounted at one end of a bell crank 3| and thearmature is attached to the other end of this bell crank which ispivoted at 32. The operation of this modification of the invention isapparent from 30 the previous explanation.

In the arrangement of Fig. 4, the lens I3 is of the cylindrical type andis provided with pivotal supports 33 and 35 about which it is rotated inresponse to vibration of the end of the armature 35 21 with which thelower edge of the lens is articulated. This rotation of the lens movesthe images 2 1 and 2E transversely of the slit 26 in accordance with theimpulses applied to the coil 23 as previously explained.

I claim as my invention:

1. A push-pull variable area sound recording system comprising a sourceoflight rays, means for defining said rays into a plurality of beams ofpredetermined shape, means for forming a 5 light slit, means forprojecting images of said beam defining means on said light slit, saidimages being oppositely disposed on each side of said slit, alight-sensitive surface, means for projecting an image of said slit tosaid light sensitive surface, and a lens intermediate said beam definingmeans and said slit forming means, said lens adapted to be vibratedtransversely of said slit to shift the light beam across said slit inaccordance with sound waves to be recorded.

2. A push-pull variable area sound recording system comprising a. sourceof light rays, means for defining said rays into a pair of light beamsof similar shape, means for forming a light slit, means for projectingimages of said beam defining means on said slit, said images beingoppositely disposed on each side of said slit, a lightsensitive surface,means for projecting an image of said slit to said light-sensitivesurface, a lens for passing light from said beam defining means to saidslit forming means, said lens being adapt- 4. An electro-magnetic lightbeam modulator comprising means for generating a substantially constantmagnetic field, a cylindrical lens mounted for oscillation about itsprincipal axis, and an armature in said magnetic field comiected to saidlens for oscillation thereof upon movement of said armature.

5. An electro-magnetic light beam modulator comprising means forgenerating a substantially constant magnetic field, a resilient bracketmember connected to said magnetic field generating means, a lens mountedon said bracket, and an armature positioned in said magnetic field andconnected to said bracket for vibrating said lens with a substantiallylinear motion.

6. A light modulator in accordance with claim 5 in which the naturalvibration period of said lens is controlled by the predeterminedresiliency of said bracket member.

FRANK E. RUNGE.

